Christine raises an interesting point about Zheng’s checklist recording Black Tern for Guangdong.
The origin of the record is almost certainly an article by E.A. Aylmer, one of the leading writers on birds in Hong Kong in the 1930s. Entitled “The English Bittern”, the article describes the breeding behavior of Great Bitterns at a bird sanctuary in Norfolk and mentions other birds seen in the Norfolk Broads, including Black Tern (Hong Kong Naturalist Vol. 7, pages 222-224, December 1936). Unfortunately, the article does not make it absolutely clear that the Norfolk Broads are in the UK, not HK!
This lack of clarity led to confusion as T.H. Cheng, the great Chinese ornithologist of his generation, understood the locality to be somewhere in Hong Kong. Thus, Black Tern appears in his list of Non-passerines in Guangdong (Cheng 1940) with the text “Hong Kong, Aylmer 1936” and again with a similar text “Hong Kong - Aylmer” in his Synopsis of the Avifauna of China (Cheng 1987). Cheng is of course a major source for Zheng’s checklists.
I don’t know of any other records of Black Tern claimed for the Guangdong-Hong Kong-Macao region which might account for the species being listed for Guangdong by Zheng. Unless other credible records come to light, the species clearly should not be on the Guangdong-Hong Kong-Macao list. The only marsh terns with certain records for the region are Whiskered Tern Chlidonias hybrida and White-winged Tern C. leucopterus.
